williemon

How can I wire up a toggle switch that will cause the torque converter to stay locked up when it might otherwise unlock? This would allow me to tow more effecentily, and with less tranny heat by letting me choose locked OD or locked 3rd depending on my needs. I could also use it when driving for my work needs. Mostly cruiseing at 30mph to 35 mph. That would also prevent tranny heating. I am going to install a cooler and temp guage, but I thought that this could give me an extra measure of saftey for the tranny that I have not ever flushed. I did just drain and add 2 gallons of tranny fluid. Last year I did a drain and refill with one gallon. I should be shot for my tranny neglect, but I now know better.

TechWrench

I suppose it could be possible to rig up a circuit to manually force the converter into lock-up, but given the circumstances you mention, I (IMHO) don't think it is a good idea. The idea of controlling heat generation by forcing lock-up seems like a good idea, but the loss of torque at lower speeds will probably hurt your performance. Also, the lock-up surface in the converter is not designed to withstand heavy torque loads, especially during towing. I think you are better off letting the trans and converter work the way it was designed, and go with the add-on cooler and possibly an external filter. Go with a good stacked plate cooler and change the fluid more often and as long as you don't have a mechanical faliure in the trans (which a manual lock-up switch wouldn't prevent) you should have no problems.

denverbikeguy

Yup. Go with the add-on cooler (bigger = better, surface area is what you want to dissipate the heat!), etc. Personally I'd let the tranny do it's job and just supplement it externally where possible. Toyota engineers are clever folk, they make good parts. It's when we go mucking with them that they break in strange new ways.

ChickenLover

Manually locking the torque converter is a pretty cool idea. However, I agree with what's been stated above - letting the truck operate how it was designed to is probably a good idea. I know you can keep 3rd locked by turning off the O/D button. When I want to pick up speed quicky on the highway I let it downshift into 3rd wait till it hits about 55-60 mph then turn O/D off, locking the torque converter - you will see the rpm's drop by about 500, then at about 70mph I'll turn O/D back on and let er' go from there. This is a very effective method IMO.

denverbikeguy

You know, I always wondered why the RPM drop happened with the O/D off. Cool! Though I seemed to get more power with it on, probably related more to engine powerband than the tranny - but I sold the Tundra and got a 5spd 4runner, so it's irrelevant now...

williemon

Ok. You all have talked me out of it. I will just add the external coolers and let the tranny handle it.

grams72

Its a good idea to add the external cooler but do not tow in O/D.
OR
You will soon be posting how to rebuil or where to buy a new tranny....